Re: [PATCH] pc: q35: Bump max_cpus to 512

[Suthikulpanit, Suravee]

Igor,

On 5/9/2022 2:12 PM, Igor Mammedov wrote:
> On Wed, 4 May 2022 08:16:39 -0500
> Suravee Suthikulpanit<suravee.suthikulpanit@amd.com>  wrote:
>
> > This is the maximum number of vCPU supported by
> > the AMD x2APIC virtualization.
> >
> > Signed-off-by: Suravee Suthikulpanit<suravee.suthikulpanit@amd.com>
> > ---
> >   hw/i386/pc_q35.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> > index 302288342a..e82b1c690d 100644
> > --- a/hw/i386/pc_q35.c
> > +++ b/hw/i386/pc_q35.c
> > @@ -357,7 +357,7 @@ static void pc_q35_machine_options(MachineClass *m)
> >       machine_class_allow_dynamic_sysbus_dev(m, TYPE_INTEL_IOMMU_DEVICE);
> >       machine_class_allow_dynamic_sysbus_dev(m, TYPE_RAMFB_DEVICE);
> >       machine_class_allow_dynamic_sysbus_dev(m, TYPE_VMBUS_BRIDGE);
> > -    m->max_cpus = 288;
> > +    m->max_cpus = 512;
> Maybe we should bump it to KVM VCPU maximum,

Grepping through the Linux kernel source, the KVM_MAX_VCPUS macro is defined 
per architecture.
AFAICT, the absolute maximum is for x86, which is 1024. Does that sound about 
right?

> and make sure we error out if asked for combination of
> hardware/irqchip is not usable.

Could you please elaborate on this part?

Thanks,
Suravee